Photoacoustic thermal characterization of electrical porcelains: effect of alumina additions on thermal diffusivity and elastic constants

Photoacoustic signal with two heating sources: theoretical predictions and experimental results for the open photoacoustic cell technique

“…The measured signal is dependent on the frequency response of the detection apparatus. Thus, a calibration or normalization function is necessary to obtain a PA signal that depends only on the sample [17,30,31,36,37]. The measured signal S can be expressed as follows [17,38,39]:…”

“…where ω c1 = 2πf c1 is the cut-off frequencies of the microphone electronics, ω c2 = 2πf c2 is the cut-off frequencies of the signal processing electronics, ω c3 = 2πf c3 is the microphone cut-off frequency, ω c4 = 2πf c4 is the microphone geometric characteristic frequency, δ c3 and δ c4 are the damping factor. In most cases, aluminum foil of thickness 10 µm is used as a reference sample [35,36] with aluminum's thermal diffusivity of 86 × 10 −6 m 2 s −1 and all other necessary physical properties being well known [15]. The TE effect is typically considered negligible in δP real when compared to the TD contribution for thin samples, and the calibration is performed by the approximation of the thermally thin regime in thermal diffusion.…”

“…The TE effect is typically considered negligible in δP real when compared to the TD contribution for thin samples, and the calibration is performed by the approximation of the thermally thin regime in thermal diffusion. The PA signal of the reference sample is adjusted in this thermally thin approach (equation ( 14)) which depends on f −1.5 [8,35,36]. Figure 4 shows simulations of the PA signal normalized for an opaque sample (equation ( 28) applied to aluminum foil in the function at room temperature.…”

On the Use of Photothermal Techniques as a Tool to Characterize Ceramic-Metal Materials

“…Here, an open photoacoustic cell (OPC) in the transmission configuration (Vargas & Miranda, 1988, Bribiesca et al, 1999) is employed to evaluate thermal diffusivity and the photothermal technique of continuous investigation illumination on the sample in a vacuum (Contreras et al, 1997) is used to measure thermal capacity density.…”

Investigação fototérmica de argila vermelha: medidas de propriedades térmicas e estruturais

“…A Fig. 2 mostra a dependência do sinal fotoacústico com a freqüência de modulação para uma amostra de alumínio [22,23].…”